One of the best ways I have of soothing my anxieties or even dread of something I would rather avoid, is to deconstruct my feelings by completing a De-catasrophising Worksheet (google it). It makes me realize the worst case scenario is unlikely to occur.

Are you in a position to limit your involvement for the Day? For instance, make only a cusory token appearance. I wonder, is your family aware of your mental health situation? I am sure they would understand if you find yourself in a position of needing to leave.

I have found that keeping myself occupied greatly helps me get through the big Day. As such, I tend to take over the kitchen. I don't neccessarily do everything, but I find myself supervising much of what happens. I find too being able to separate myself from everyone by standing behind the kitchen island to also be of great healp. I limit the time I am present. We eat for 3pm. I arrive about 2pm and leave right after the clean-up is complete. I am fortunate that my family is greatly understanding. I admit that there were a few years that all didn't work out so well despite the above suggested efforts. There was one year I locked myself in a spare room.